This invention relates generally to electric lamps, and particularly to those for use on motor vehicles such as, typically, headlamps. Still more particularly, the invention pertains to improvements in aiming mechanisms for aiming and retaining headlamps or the like in the proper position with respect to the vehicle,
Aimable headlamps may be divided into two broad designs according to the member to be tilted, both vertically and horizontally, for aiming the headlamp. In one such design the complete headlamp unit, including an electric lighting bulb or bulbs, a reflector or reflectors and a lens, is tilted relative to the vehicle or to the lamp housing fixed to the vehicle. The other design is such that only the reflector is tilted relative to the lamp body or the like which is fixed to the vehicle.
In either case, a typical aiming mechanism is composed of a pivotal connection such as a ball-and-socket joint between a tillable member and a fixed member, and two aiming screws extending between the two members. The relative placement of the pivotal connection and the aiming screws is such that the tightening or loosening of the first of the two aiming screws results in the tilting of the tillable member about an axis passing through the pivotal connection and the second aiming screw in a plane at right angles with the lamp axis. Similarly, the manipulation of the second aiming screw results in the tilting of the tiltable member about an axis passing through the pivotal connection and the first aiming screw in the same plane as above.
A problem has been encountered with aiming mechanisms of the foregoing general construction, particularly when they are applied to headlamps of horizontally elongated shape which are currently favored in passenger cars. When tightened or loosened, the aiming screws do not move linearly, but arcuately about the noted axis. Such arcuate movement of the aiming screws inevitably imposes torsional stresses thereon. Such torsional stresses can easily cause the deformation or, in the worst case, destruction of the screws themselves or of the parts coupled thereto, either directly or indirectly, because all such parts were fabricated from rigid materials. The deformation of the reflector in particular is highly undesirable as it directly affects the optical performance of the headlamp.
Such deformation or destruction has been more likely to occur with the horizontal aiming screw, which is spaced a greater distance from its axis of arcuate movement than is the vertical aiming screw from its axis when the headlamp is elongated horizontally. The greater this distance is, the travel must the screw travel for tilting the tiltable member through a given angle, and, consequently, the greater is the risk of ruining the screw or other associated parts.
It might be contemplated to make the distances in question as short as possible so that the tiltable member might tilt a desired angle with slight travel of the aiming screws. This solution is objectionable because the screws should be spaced as far away as practical from their axes of the arcuate displacement for the reduction of manual forces required for turning them.